1. Field of the Invention
The present invention relates to an image forming apparatus, image forming method and program, especially relates to an image forming apparatus, image forming method and program which receives a structured document data such as PDF data and forming an image.
2. Description of Related Art
So far, a network type printer has become common, which prints a print data stored in a computer such as a PC through a network such as a LAN. In this case, generally, print data is sent after a printer driver installed to a computer converts the print data to one prescribed in a page description language which the printer can analyze such as POSTSCRIPT®. The printer performs a series of the image forming process in round-robin fashion which is to alternate receiving the converted print data and executing the other process such as image processing for the received print data at predetermined interval.
On the other hand, a structured document data such as PDF (portable document format) has become common as a print data distributed on the Internet, in which the original document can be reconstructed from the structured document data independently from a type of OS (operation system) and application. In particular, PDF data includes an object to draw a part or all of a content of a certain page of a document. The objects may be arranged in a file independently from the sequence thereof displayed in the document. A structure of the document is analyzed by referring to location information of the object in a file, information about the object included in a content of each page, and the like. In recent years, a printer which can directly print PDF data sent from a PC or the like without converting it to print data (hereinafter referred to as a direct print) has become common along with dissemination of such PDF data.
The above-described PDF data records a document structure information designating a location of objects constituting each page of the document at the end part of the PDF data. Here, a data structure of a PDF data is described with reference to FIG. 6. A PDF data is composed of a header part including data attribute of the PDF data, an actual data part including data to be printed, and a document structure part including document structure information of the PDF data. Generally, when PDF data is sent, the header part, actual data part and document structure part is sent in that order. Thus, a printer cannot start printing before the printer receives whole parts of the PDF data.
Therefore, it has been proposed that PDF data is divided into at least three data blocks, and the PDF data is sent to a printer sequentially from the divided last data blocks (see JP 2004-348194A, JP 2004-348423A and JP 2004-348431A, hereinafter also referred to as patent document 1, 2 and 3 respectively). Further, it has been proposed that PDF data is edited and reconstructed so as to be new PDF data of each page and the reconstructed PDF data is sent to a printer (JP 2004-348498A, hereinafter referred to as patent document 4).
However, in above-described patent documents 1 to 4, a host apparatus to send PDF data to a printer such as a PC requires a member to process the PDF data, and also the printer requires a member to deal the processed PDF data. Thus, it has been problematic that the host apparatus and the printer have increased loads.